1. Field of the Invention
The present invention relates to a magnetic sensor capable of detecting a change in a magnetic field with high sensitivity, and a method of manufacturing the magnetic sensor.
2. Description of the Related Art
As a magnetic sensor for detecting the direction of a micro magnetic field such as geomagnetism, there has been known one using an anisotropic magnetoresistive element formed of a ferromagnetic material such as permalloy (for example, refer to Japanese Patent No. 3318762 and Japanese Unexamined Patent Application Publication No. Hei 6-174471).
Recently, there has been developed a magnetic sensor provided with a plurality of giant magnetoresistive elements (GMR) exhibiting higher detective sensitivity to a change in a magnetic field than the anisotropic magnetoresistive effect element (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-66127). In this type of the magnetic sensor, a bridge circuit is configured by, for example, four GMR elements, and when a micro magnetic field to be detected (hereinafter referred to as a “detected magnetic field”), the resistances of certain two GMR elements are changed in the positive direction and the resistances of the remaining two GMR elements are changed in the negative direction. The magnitude of the detected magnetic field can be measured by detecting a difference in the resistance change of each GMR element (a differential output).